Relatively thin-walled cylinders are typically produced by the conventional manufacturing operation known as spinning wherein a pipe section is placed in the hollow spindle of a lathe-type machine after having been heated and wherein the pipe section is spun about its longitudinal axis while a tool is fed against the pipe section to form the ends of the cylinder.
A cylinder for containing and transporting various gases at high pressures (e.g., 1800 to 3000 psig or higher) must have sufficient integrity to withstand the stresses of the pressurized gas contained within the cylinder. Further, any failures shall all be in the ductile mode and shall not cause the cylinder to fragment. In the United States of America, the Department of Transportation has promulgated specifications and regulations governing the manufacture and use of such high pressure cylinders.
Heretofore, the integrity of the high pressure cylinders and compliance with the Department of Transportation specifications could only be ensured with cylinders of seamless construction. The manufacture of seamless tube or pipe is well known and involves relatively expensive methods to produce a product that does not have a longitudinal seam. Examples of specifications governing the construction of seamless high pressure cylinders are the U.S. Dept. of Transportation specifications set forth in 49 CFR 178.36 and 49 CFR 178.37.
Although seamed pipe and tubing can be less espensively produced than seamless pipe or tubing, cylinders formed from seamed pipe or tubing must be carefully manufactured, examined, and tested to ensure their integrity. Typically, seamed pipe has the longitudinal seam formed by electric resistance welding. In high pressure applications, the welded seam must be free of critical defects that could lead to failure of the cylinder.
Heretofore, conventional manufacturing techniques for producing cylinders from electric resistance weld seamed pipe were not of a quality sufficient to lead to acceptance of such seamed cylinders for high pressure gas applications. Further, heretofore, examination and testing techniques had not been developed to the extent believed to be necessary to permit the use of a tested seamed cylinder in high pressure applications.
It would be desirable to provide a cylinder fabricated from electric resistance weld seamed pipe or tube for use in high pressure applications. Further, it would be desirable to provide methods for manufacturing, examining, and testing such a cylinder that would ensure the integrity of the cylinder with respect to use with high pressure gas.